package com.king.designpatterns.hybriddesignpattern.hybriddesignpattern.chainofcommandandresponsibility;

import java.io.File;
import java.io.IOException;
import java.net.URL;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Enumeration;
import java.util.List;

/**
 * @author king
 * @date 2021-06-11 15:19
 */
public class ClassUtils {
    public static List<Class> getSonClass(Class abstractClass) {
        // 定义一个返回值
        List<Class> returnClassList = new ArrayList<>();
        // 获得包名
        String packageName = abstractClass.getPackage().getName();
        // 获得包中的所有类
        List<Class> packClasses = getClasses(packageName);
        
        // 判断是否是子类
        for (Class c : packClasses) {
            if (abstractClass.isAssignableFrom(c) && !abstractClass.equals(c)){
                returnClassList.add(c);
            }
        }

        return returnClassList;
    }

    /**
     * 从一个包中查找出所有的类，在jar包中不能查找
     *
     * @param packageName
     * @return
     */
    private static List<Class> getClasses(String packageName) {
        ClassLoader classLoader = Thread.currentThread().getContextClassLoader();

        String path = packageName.replace('.', '/');
        Enumeration<URL> resources = null;
        try {
            resources = classLoader.getResources(path);
        } catch (IOException e) {
            e.printStackTrace();
        }
        List<File> dirs = new ArrayList<>();
        while(resources.hasMoreElements()){
            URL resource = resources.nextElement();
            dirs.add(new File(resource.getFile()));
        }
        List<Class> classes = new ArrayList<>();
        for (File directory : dirs) {
            classes.addAll(findClasses(directory, packageName));
        }

        return classes;
    }

    private static Collection<Class> findClasses(File directory, String packageName) {
        List<Class> classes = new ArrayList<>();
        if (!directory.exists()){
            return classes;
        }

        File[] files = directory.listFiles();
        for (File file : files) {
            if (file.isDirectory()){
                assert !file.getName().contains(".");
                classes.addAll(findClasses(file, packageName + "." + file.getName()));
            }else if(file.getName().endsWith(".class")){
                try {
                    classes.add(Class.forName(packageName + "." + file.getName().substring(0, file.getName().length() - 6)));
                } catch (ClassNotFoundException e) {
                    e.printStackTrace();
                }
            }
        }
        return classes;
    }

}
